Cue throw using side

[Dave_marsy]

Why do cues throw the ball when using side ...my old cue used to push the cue ball to the left when using right hand side but when the spin griped the cloth moved to the right ...or when using left hand side throw to the left but recover and swing to the right after the spin grips the cloth .....I’m playing running side in both cases

I know this happens when going against the nap...but I’m getting this problem going with the nap

I just got a new cue and when using right hand side it just goes to the left and never comes back ...I find this very hard to allow for ....
Any idea why ..is it the cue the tip size or the tip ?